Generally, measurement of the concentration of fine particles is one of the most frequently conducted procedures in biological, food, and environmental fields. Particularly, a concentration measurement experiment in a medical field is very usefully employed to diagnose patients' health using the number of erythrocytes or leucocytes in the blood. Currently, a Hemacytometer and a Coulter Counter are frequently used as devices for measuring the concentration of fine particles.
The hemacytometer is a device in which a lattice is formed on a glass slide, and the number of fine particles and the volume of the lattice are used to measure a concentration. It is most frequently employed because it has a low-priced chip and a small size. However, this device is disadvantageous in that, since an operator must count the number of fine particles in the lattice one by one using a microscope, precision and efficiency are poor.
The Coulter counter capable of avoiding the disadvantages of the hemacytometer is disclosed in U.S. Pat. Nos. 4,030,888 and 4,307,339. According to the measurement principle of the Coulter counter, the number of fine particles is computed using a change in resistance which is caused by the difference in electrical conductivities of the fine particles and a buffer, and the amount of fluid passing through the buffer is precisely measured to obtain the concentration of fine particles. Hence, the Coulter counter must be equipped with a pump that is capable of transmitting a precise amount of the fluid to the buffer, and it is very important to precisely control the pump. Therefore, the Coulter counter is disadvantageous in that, since the precise pump and many accessories for controlling it are necessary, its price is high.